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SAE-AISI 8740 Steel vs. 7129 Aluminum

SAE-AISI 8740 steel belongs to the iron alloys classification, while 7129 Aluminum belongs to the aluminum alloys. There are 30 material properties with values for both materials. Properties with values for just one material (1, in this case) are not shown. Please note that the two materials have significantly dissimilar densities. This means that additional care is required when interpreting the data, because some material properties are based on units of mass, while others are based on units of area or volume.

For each property being compared, the top bar is SAE-AISI 8740 steel and the bottom bar is 7129 Aluminum.

Metric UnitsUS Customary Units

Mechanical Properties

Elastic (Young's, Tensile) Modulus, GPa 190
69
Elongation at Break, % 11 to 23
9.0 to 9.1
Fatigue Strength, MPa 270 to 350
150 to 190
Poisson's Ratio 0.29
0.33
Shear Modulus, GPa 73
26
Shear Strength, MPa 370 to 400
250 to 260
Tensile Strength: Ultimate (UTS), MPa 580 to 670
430
Tensile Strength: Yield (Proof), MPa 380 to 570
380 to 390

Thermal Properties

Latent Heat of Fusion, J/g 250
380
Maximum Temperature: Mechanical, °C 410
180
Melting Completion (Liquidus), °C 1460
630
Melting Onset (Solidus), °C 1420
510
Specific Heat Capacity, J/kg-K 470
880
Thermal Conductivity, W/m-K 39
150
Thermal Expansion, µm/m-K 13
24

Electrical Properties

Electrical Conductivity: Equal Volume, % IACS 7.3
40
Electrical Conductivity: Equal Weight (Specific), % IACS 8.4
120

Otherwise Unclassified Properties

Base Metal Price, % relative 2.6
9.5
Density, g/cm3 7.8
2.9
Embodied Carbon, kg CO2/kg material 1.5
8.3
Embodied Energy, MJ/kg 20
150
Embodied Water, L/kg 50
1150

Common Calculations

Resilience: Ultimate (Unit Rupture Work), MJ/m3 71 to 120
37 to 38
Resilience: Unit (Modulus of Resilience), kJ/m3 390 to 850
1050 to 1090
Stiffness to Weight: Axial, points 13
13
Stiffness to Weight: Bending, points 24
47
Strength to Weight: Axial, points 20 to 24
41
Strength to Weight: Bending, points 20 to 22
43 to 44
Thermal Diffusivity, mm2/s 10
58
Thermal Shock Resistance, points 17 to 20
19

Alloy Composition

Aluminum (Al), % 0
91 to 94
Carbon (C), % 0.38 to 0.43
0
Chromium (Cr), % 0.4 to 0.6
0 to 0.1
Copper (Cu), % 0
0.5 to 0.9
Gallium (Ga), % 0
0 to 0.030
Iron (Fe), % 96.5 to 97.7
0 to 0.3
Magnesium (Mg), % 0
1.3 to 2.0
Manganese (Mn), % 0.75 to 1.0
0 to 0.1
Molybdenum (Mo), % 0.2 to 0.3
0
Nickel (Ni), % 0.4 to 0.7
0
Phosphorus (P), % 0 to 0.035
0
Silicon (Si), % 0.15 to 0.35
0 to 0.15
Sulfur (S), % 0 to 0.040
0
Titanium (Ti), % 0
0 to 0.050
Vanadium (V), % 0
0 to 0.050
Zinc (Zn), % 0
4.2 to 5.2
Residuals, % 0
0 to 0.15